Grinding cement materials, etc.



' June 10,1930. ,c. PONTQPPIDAN 1,

GRINDING CEMENT MATERIALS ET G Filed Dec. 50. 1927- 10 If the temperature,

adhere Patented June 10, d

UNITED STATES PATENT; OFFICE CARL PONTOPPIDAN,

OT COPENHAGEN, DENMARK, ASSIGNOR TO I. II SEIDTH & CO.,

] NEW YORK, N. Y., A CORPORATION 01 NEW JERSEY GRINDING CEMENT MATERIALS, ETC.

Application filed December 30, 1927, Serial K9.

Experience has shown that in the grinding of cement and kindred materlals, the temperature at which the rinding process is effected has a considera le'influence on 5 the fineness to which the cement or the like can be ground and on the propertles thereof, and that this influence is particularly pronounced in cases in which it isrequired to grind the material very fine.

grinding mill in which the grindin of cement material, for instance, is efiecte exceeds about 100 C. the round materlal has a tendency to clog or ad ere to the surfaces of the mill and of the grinding bodies, etc.

with which the material comes in contact during the grinding and, consequently, the

effectiveness of the grinding bodies is reduced during their operation upon the material to be ground, to such an extent that at this higher temperature they are unable to grind the same quantity of material to the same degree of fineness as at lower temperatures, at -which the material does not to the grinding bodies.

Since the power required for driving the grinding mill remains substantially the same whether the grinding is performed more or less efiiciently, the clogging of the material to be ground on the grinding bodies and grinding efficiency of the mill to a considerable extent.

A series of practical experiments with various kinds of grinding mills has shown that the efficiency of the mills may be as much as 33% lower at the higher temperatures at which clogging occurs than in cases oflower temperatures at which no clogging occurs.

In addition to the clogging of grinding 1 bodies and grinding surfaces by the material I cated above has a time of .setting which is considerably shorter than is admissible for standard sound cement, so that the rise of in the portion of the rounded for this purpose by a cooling-.

surfaces actually reduces the 243,530, and in Great Britain October 8, 1927.

templeraturehas a directly injurious efiect, on t e quality of the cement.

In'order to eliminate the troubles due to a high rise of temperature it has been proposed heretofore to sprinkle the grindin mill externally with water during the grin ing process. This procedurefhowever, requires very considerable quantities of cooling water, and in many cases the grinding mill, such as a tube-mill, must be surjacket, which causes considerable inconven 1ence as regards accessibility of the grinding mill for inspection and the like.

It has also been proposed, mstead of sprinkling the grinding machine with water,

to addwater, prior to the grinding, that is,

before the material enters the mill, to the action taking place between theadded water and the material to be ground, so that the water may combine with the cement dust during the first stage of the grinding process and clog the passages, etc. of the grindin mill.

Although the limited quantity of water which may be added to a material before grinding may assist in reducing the temperature during the first stage of the grinding process, it will not prevent the temperature of the material to be ground from increasing to such an extent, during the last stage of the grlnding in which a reduction of the rise of temperature is of greatest importance, as to prevent the above mentioned ,difiiculties from being created. The quantity of water addedbefore grinding will in fact'partly' evaporate and'partly combine with the dust formed by the material to be ground, so that no water will be left to bind, that is, to absorb, by its evaporation, a sufiicient portion of the heat developed'during the subsequent and final part of the grinding process to reduce the temperature. This is particularly true when the material is to I I mill, but it may be fitted freely through the,

be ground to a very high degree of fineness as the amount of heat produced during the last stage of such grinding is very large, and the material to be ground is more 1nclined to adhere to the grinding surface the hi her its degree of fineness.

he present invention has for its object to overcome the difliculties referred to and it accomplishes this purpose by the addition to" the material to be ground, of an evaporable substance such as liquid in such manner that when it is exposed to the action of the heat produced by the grinding operation it will, by its eva oration, bind or absorb so much heat that the material will be cooled to a temperature below the critical temperature of the particular grinding process, that is, the temperature at which the material shows an appreciable tendency to adhere to the surfaces of the mill and of the grinding bodies with which it comes into contact.

By reason of the large quantity of heat required to evaporate the added substance, such as water, the quantity of the added substance required' will be relatively small,- as a rule only about one to three per cent of the weight of the material ground. For this reason the present process becomes very much simpler and more convenient to carry out than the processes known hitherto. The

quantity of evaporable substance is measured previously to being added or while being added, and is conveyed to the grindingmill in any suitable manner as through a suitable pipe line which, in case of tube-mills for example, may be introduced through one of 'the end trunnions of the mill, preferably through the trunnion provided at the discharge end of the mill. If the supply pipe is inserted through an end trumiion, it will not be necessary to connect it rigidly to the trunnion and a hole in the end screen of the mill. .In tube-mills the supply pipe may be passed axially into the mill through the inlet end of the latter or, more suitably,

through the outlet end, and may then pass either axially through the mill or along the inner or outer wall of the same to the point where it is desired to supply the liquid.

At this point the supply pipe may terminate,

if desired, in a spreader or atomizing device whereby the liquid is atomized or spread into the mill and, consequently, may be dis tributed quickly overthe interior of the desired part of the mill.

The accompanying drawing shows diagrammatically two dlfierent embodiments of the invention. I

Figure 1 is an outline view in longitudinal 'section of a tube-mill in which the supply of liquid is effected through the discharge end of the mill, and I Figure 2 is a similar view of a tube-mill ated with it a storage bin 0) from which cement clinker for example is fed to the mill by means of a feeder table b and a supply funnel a. The finished ground cement passes out of the mill r throu h one of the end trunnions d and a control ing screen e, and then falls throu h a pipe f on to a conveyor, not shown. t g is indicated an exhaust flue for the vapor generated in the mill in consequence of the-addition of water to the same, as hereinafter described.-

In .the construction shown in Figure 1 wateris introduced into the last Funding chamber III of the mill by means 0 a tube I inserted through the end trunnion (i into the grinding chamber III and connected, at its outer end, to a pump 7' which is supplied with water through a pipe 71 from a'pipe h, fitted with regulating valve '0. The pipe Z is provided with a packed joint is, and at the end of the pipe Z, inside of the mill, is a spreader m or the like. The pipe Z may be supported in the mill, with which .it rotates, by means of rods n. By means of the spreader m water in a finely divided or preferably atomized state is supplied constantly and in small quantity to the grinding bodies in the grinding chamber III, and by the absorption of heat in its evaporation the temperature in the said chamber is maintained within suitable limits.

The temperature of the material leaving the mill may be observed by means of a contact thermometer p inserted in the pipe f.

The material directed from the bin 0 into the mill may also pass a contact thermometer 0 in the dischargespout of the'bin to indicate the temperature of the material supplied to the mill.

- Through the proper functioning of the contact thermometers 0 and p it can be de- 1 termined when the permissible temperature limits have been reached, and therefore when an increase or reduction in the addition of liquid is required in order to maintain the temperature of the material within definite 1 limits. I v

The general arrangement of the construction shown in Figure 2 differs from that shown in Fi re 1 merely in that the supply of liqui is effected through the inlet end of the mill. After hav'in passed the pum j and the-packed joint the liquidsupp ypipe Z passes through the end trunnion t at the inlet end of the mill, and is then extended radially out through the lata spreader or atomizer m attached, centrally of the mill, to the last portion 8 of the liquid-supply pipe which is extended diametrically across the mill.

In cement grinding it is desirable to supply the liquid or other evaporable substance at av point in the mill where the temperature differs only slightly from the temperature, as a-rule 100 C., at which the substance evaporates. However, since the substance, particularly a liquid, will generally be distributed over a large area within the grinding machine when it is supplied thereto, it

would be only approximately correct to refer to a definite temperature of the material or to a definite point of the mill at which the supply of liquid is to be efiected. It would be more correct to refer to a zone of supply. In tube-mills for grinding cement the location of this zone depends upon many different 'factors, such as the temperature of the clinker supplied to the mill, the quantity,

the material treated etc.

principle it may even be desirable to sup-- ply the liquid in several different zones. For instance, if the mill has three chambers, then the liquid may be supplied to the second and third chambers, while under other circumstances it may be adyantageous to supply the liquid to two different zones of one and the same chamber, such as the third chamber.

' of heat in the'evaporation of the liqui' temperature of the material being ground is evaporated without absorption by the material.

2. The improvement 1n the grlnding of cement material, which consists in addin to the material while it is being ground a iquid evaporable by the heat developeddn grinding, whereby, through the absor tuliln t e reduced, the liquid being added in such quantities and when the temperature of the material is such that the liquid is evaporated without absorption by the material.

This specification signed this 10th day of December, A. D.- 1927 v CARL PONTOPPIDAN.

Substances which for some'reason or other are desired to be mixed with the ground material may be added to the same together with the substanceused for cooling the material. Suchother substances, in the case of cement grinding, such as chloride of lime, sulphate of lime, tannin and other known admixtures, may suitably. be s spended or dissolved in the evaporable liquid before the "latter is introduced into the mill.

I claim as'my invention: 1. The improvement in the grindingof cement material, which consists in adding to the material while it is being ground a substance evaporable by the heat developed in grinding whereby, through the absorption of heat in the evaporation of such substance,

the temperature ofthei material being;

ground is reduced, the substance being added in such quantities and when the temperature of the material is such that the substance is a 

